Dental alignment is widely being used for treating malocclusion or for cosmetic purposes. A widely used apparatus based on the related art is the so-called fixed braces, which involve affixing brackets onto the teeth and coupling wires to the brackets to pull or push the brackets for dental alignment.
In fixed braces, the brackets are usually mounted onto the smooth outer surfaces, i.e. the labial side, of the teeth. While such fixed braces provide advantages in terms of effectiveness and convenience of the procedure, patients may often be averse to using braces because of the lowered aesthetic appeal, as illustrated in FIG. 23.
In addition to the problem of fixed braces having a negative aesthetic effect, there also other problems such as the inconvenience of having the braces affixed all the time. To resolve such problems, transparent aligners (and procedures) such as Invisalign and Clear-aligner have been proposed. Both of the above are aligners having transparent forms and may be worn in the manner of a mouthpiece.
The former entails dividing the transformation process between the current state and the target state of the teeth into several dozens of stages. After molding pockets that match the dental arrangement for each stage, the patient would wear the dental pockets, replacing the pockets for each stage. The latter is similar to the former, but is differentiated in that progress is observed and the pockets are fabricated as necessary.
The procedure using transparent aligners was developed in 1997, with the launching of the dental aligner “Invisalign System” by the U.S.-based company “Align Technology, Inc.” Details may be found in U.S. Pat. No. 5,975,893 and No. 6,217,325 held by the company mentioned above. The “Invisalign System” creates 20 to 30 pairs of mockups for the stages the teeth must progress through until they ultimately reach the desired positioned, using a special program to obtain a virtual simulation based on 3-dimensional scans of the patient's teeth. Afterwards, transparent plastic casts are fabricated according to each of the mockups and provided to the patient, where the plastic casts allow movement of the teeth.
The feature of the “Invisalign System” is to gradually move the misaligned teeth to their final target positions by fitting the teeth into a series of plastic casts according to the corresponding stages. Since the plastic casts are made from a transparent material and are not readily visible, they have minimal negative impact on a patient's daily social life. Another advantage is that the aligner can be easily removed and reinserted as needed by the patient.
With such transparent alignment method, an aligner of a transparent material (hereinafter referred to as a transparent aligner) is capped onto the teeth like a mouthpiece, so that it is not readily discernible from the exterior. Moreover, it can be removed and reinserted at will, allowing greater convenience. Due to these advantages, this method is gaining more popularity compared to other alignment methods.
However, although the existing transparent aligner may be great for pulling or pushing teeth, it cannot apply a strong rotating force on the teeth, so that it is ineffective for rotating correction. In particular, the concave portion at the upper part of the teeth mockup may apply a greater force on the teeth compared to other portions, making it difficult to apply rotational correction on the teeth.
Also, with the existing transparent aligner, it may not be easy to remove the aligner if the teeth are severely crooked or if the aligner is too tight, incurring problems such as broken finger nails or damaged gums.
Furthermore, the existing transparent aligner may be limited in terms of application to children or adolescents as it does not provide space for a developing permanent tooth before or after a primary tooth is shed.
Also, the existing transparent aligner has a specific thickness. Thus, when it is needed to move the teeth by a large amount or a wearer needs to wear the aligner for an extended period, the aligner may cause pain, or the aligner may not function properly due to abrasion.